How do Potholes Form?
Sun, heat, and vehicle loads can break down roads, but the biggest enemy of a road is water. When water gets underneath the pavement, the road becomes weaker. As vehicles use the road, the saturated, weakened parts of the pavement start "pumping" up and down, and a pothole is born.
Seal coats and resurfacing are the most common types of surface treatments we use.
A seal coat is less expensive than resurfacing, and keeps water from penetrating the surface of the roadway. The two types of seal coats most commonly recommended by DPW are Fog Seals and Chip Seals.
Fog seals are simply a sprayed-on liquid asphalt film that seals the pavement surface.
Chip seals have a layer of small rocks placed over a thick coat of liquid asphalt. The rocks stick to the asphalt film and make a rougher surface that provides better traction to prevent skidding. Chip sealed roads are lighter in color than fog sealed roads.
Fog seals and chip seals are placed on roads that still have enough structural strength to withstand the weight of traffic. For deteriorating roads that are losing this strength, more extensive resurfacing is required.
Most resurfacing is done with Asphalt Concrete (AC), a hot mix of paving grade asphalt, sand and varied grades of crushed rock. Resurfacing can include a paving fabric if needed, depending on the condition of the old asphalt. Paving fabric is placed on top of the old asphalt to keep existing surface cracks from "reflecting" through to the new asphalt. AC is applied in varying thicknesses, determined by how much the road has deteriorated and traffic loads. Each increment of thickness makes the road stronger. The cost is higher for each inch of asphalt needed.
Crack seals may give the road a crazy jigsaw look, but they are good at preventing water from flowing through pavement cracks. This treatment will prolong the life of the pavement, making our maintenance dollar more effective.